Coil steel and other metals come from the manufacturing plant in rolls or coils. The metal typically has a crown; that is, the metal is thicker in the center than at the edges. The coil is unwound, slit into ribbons and rewound. Because the center ribbons are thicker than the edge ribbons, the edge ribbons are typically longer and have a tendency to be loose when rewound. A loose coil is undesirable because looseness or uneven tension interferes with the metal processing which requires even tension to produce uniform results without undue wear on the processing equipment.
A component of a slitting line for a metal coil is a tension stand which is typically two wooden boards attached to a metal frame and covered with felt or similar material that is wider than the pre-slit coil. Pneumatic or hydraulic cylinders open and close the wooden boards to pinch the metal after slitting. As the metal is rewound, the longer ribbons accumulate slack in a pit. A problem with this process is attaching the felt to the boards.
In the past, the felt attached by nailing or stapling which worked reasonably well except that different types of metal (stainless steel, aluminum, cold rolled steel, hot rolled steel, etc.), textures (polished, embossed, motorlam, etc.) and finishes (painted, galvanized, etc.) caused a need for the felt pad to be replaced frequently, sometimes after each coil. The felt would either wear away or become contaminated with dirt and debris causing metal damage. Removing the nails or staples was time consuming and the wood needed to be replaced frequently due to the constant damage caused by the nails and staples.
One solution to the problem of replacing worn or damaged boards and pads was to use a board with hook and loop fasteners to secure the felt. The hook portion of a hook and loop fastener was glued to the board and the felt pressed onto it. While the felt could be easily removed for replacement, the adhesion was not very good. In addition, the friction of the metal passing through the felt pads created heat sufficient to soften the glue causing a loss of adhesion and failure.
A plastic saddle was developed to solve the wood to fastener adhesion problem. A special heat resistant adhesive was used to bond the hook fastener to the saddle. The saddle would fit over the top of the wooden board and had holes for screws to secure it to the board. Although the saddle improved metal slitting operations, there was still a problem because the hook fastener did not grip the felt sufficiently.
Also, the metal coils sometimes had defects, such as a line stop that could snag the felt, or a weld across the width of the metal where two coils are joined. For galvanized steel, a line stop forms during manufacturing where the line stops but the coating of zinc continues and forms a build-up or lump. When a line stop or weld travel through the tension stand, it will usually snag on the felt pad ripping the pad off the hook fastener, and sometimes destroying the saddle. Accordingly, it will be appreciated that it would be highly desirable to have a tension board that securely holds the felt pad without nails, staples or glue, and which facilitates rapid changing of the pad.